18.3.1: Diagnostic methods and cycle manipulation in the mare Flashcards
True/false: a mare in the transitional period may stand to be bred/ appear to be in oestrus.
True
In late autumn, the mare’s cyclicity often ends with…
A silent or anovulatory heat
Some ponies cycle throughout the winter.
What are signs of the transitional period?
- Mare may show oestrus behaviour
- Mare may stand to be bred
- Mare has follicles that grow and regress (not enough LH or LH-receptors) but these do not ovulate
- Ovaries may be large with palpable follicles
The breeding season starts ~15th Feb so shortening the transitional period is necessary. How can this be achieved?
- Providing 16hrs artificial light and additional nutrition from 1st Dec
- (Some clinicians also administer GnRH at this time; efficacy unproven)
- Once the mare is in the transitional period (follicles greater than 25mm in diameter) -> progestogens are administered to suppress the release of LH
- This is in the form of altrenogest (Regumate) given in feed for ~10 days
- Follicles grow during progestogen treatment
- When follicles reach 45mm progestogen treatment is stopped and there is a release of LH which induces ovulation
- (Some clinicians also give GnRH at this time to enhance the LH surge)
What 3 things can we used the manipulate the transitional phase?
- Light
- Progesterone/ progestogens
- GnRH
What can we use to hasten ovulation in mares that are in oestrus?
- GnRH
- hCG (this is LH-like in activity)
When it the optimal mating time in mares?
- Optimum mating = 24-48hrs before ovulation -> this means the sperm is in the tract waiting for the egg
- Mares ovulate a secondary oocyte that is immediately fertilisable but remains viable for only 12hrs after ovulation
Signs of approaching ovulation on ultrasound
- Follicle size (~40-50mm)
- Follicle softening
- Follicle wall thickened
- Follicle haemorrhage
- Follicle pointing
- Reduction in uterine oedema
What can we use to induce return to oestrus when the mare is cycling but in the luteal phase?
Prostaglandin
Describe the characteristics of repro tract when the mare is in anoestrus
Anoestrus
* Ovaries: small and hard, with small follicles
* Uterus: flaccid
* Vagina: pale and dry
* Cervix: small and closed
Describe the characteristics of the repro tract when the mare is in the transitional phase
Transitional phase: irregular cycles, long oestrus
* Ovaries: larger - soft follicles that grow and regress
* Uterus: transitional
* Vagina: like anoestrus
* Cervix: like oestrus
Describe the characteristics of the repro tract when the mare is in oestrus
Oestrus
* Ovaries: medium with either follicle or corpus haemorrhagicum present
* Uterus: large and oedematous
* Vagina: moist and hyperaemic
* Cervix: broad and soft
Describe the characteristics of the repro tract when the mare is in dioestrus
Dioestrus
* Ovaries: medium sized, early CH feels like follicle. CL not palpable.
* Uterus: small and tonic
* Vagina: pale and dry
* Cervix: hard and narrow
Describe the characteristics of the repro tract when the mare is pregnant
Pregnant
* Ovaries: early on, these are medium-sized, but become very large when eCG is secreted
* Uterus: tonic and pregnancy swelling can be detected from 21 days
* Vagina: pale and dry
* Cervix: hard and narrow
What bacterial venereal pathogens do you screen for in the mare? What disease do these organisms cause?
- Taylorella equigenitalis
- Klebsiella pneumoniae
- Pseudomonas aeruginosa
These organisms cause contagious equine metritis -> the mare does not get pregnant. They do not cause late abortion.
You have taken a clitoral sinus and clitoral fossa swab and want to test for Taylorella - what transport do you use and why? When must your sample reach the lab?
- Taylorella is microaerophilic so has to be held at low oxygen -> transport in charcoal
- Must arrive at lab promptly - do not swab on Friday or Saturday, do not want to get stuck in post
What should you do if CEM is isolated in mares prior to covering?
- Isolate and treat infected mares
- Notify owners of mares
What should you do if CEM is isolated in stallions prior to covering?
- Isolate and treat stallions
- Notify owners of mares that covering may not be taking place as planned
What should you do if CEM is isolated in mares and stallions after covering?
- Cease covering
- Check all mares implicated in the outbreak
- Do not cover until 3 negative swabs each at least 2 days apart
What viral venereal pathogens do we screen for in mares?
- Ensure the mare is serologically negative to Equine Viral Arteritis (EVA)
How is Equine Viral Arteritis transmitted?
- Via respiratory tract route
- Venereally including in chilled semen
Clinical signs of Equine Viral Arteritis
- Flu-like with significant conjunctivitis (pink eye), focal dermatitis, limb and ventral oedema
- Pregnant mares may abort
- Aborted foetuses appear partially autolysed (compared to fresh foetus in EHV) but still need appropriate pathological exam and testing
Which animals can become persistently infected with Equine Viral Arteritis?
- When stallions are infected with EVA, it can infected the accessory glands and result in persistent infection
- Mares clear the infection within 1 month and develop immunity
True/false: Equine Infectious Anaemia is notifiable.
True
What non-venereal pathogens might we screen/ plan for in an animal coming to stud?
- Equine herpes virus 1 -> plan vaccination for months 5, 7 and 9 of pregnancy
- Equine herpes virus 3 (equine coital exanthema) - inspect and ensure negative
- Equine infectious anaemia (EIA) -> ensure horses returning to the UK are serologically negative
- Strangles - quarantine on entry to demonstrate no signs develop
When would you take uterine swabs in the mare?
- For bacterial venereal pathogen screening
- In cases of endometritis
- For endometrial bacteriology (in endometritis) to allow C&S
- For the detection of other pathogens e.g. yeast, fungi
When would you not expect to find bacteria in the uterus?
- In the luteal phase - the cervix is closed so this would be significant if found
- However uterine swabs are often taken during oestrus (HBLB guidance) when the cervix is open and you might find bacteria
If a mare has a Category I endometrial biopsy, what does this mean for her estimated foaling rate? What about a Category III mare?
Endometrial biopsies
* Category I - no pathological changes and should have normal fertility; estimated foaling rate 80-90%
* Category III - severe endometrial changes; uterus may be incapable of supporting foetal development. Estimated foaling rate <10%
What term is given to this phase?
Transitional phase
What phase of her cycle is this mare in?
Oestrus
Large volume of uterine fluid in a pyometra
Typical appearance of a mare CL
Abnormal CL with honeycomb appearance:
This is an anovulatory luteinised/ haemorrhagic follicle commonly seen at the end of the breeding season in older mares
This mare has been barren for more than 2 seasons. She was served at a professional stud with appropriate veterinary management. She presents with fluid in her uterus shown below. What conclusions can you make about the likelihood of getting her pregnant?
- This mare has long-term fluid accumulation in the uterus typical of chronic endometritis -> she has got chronic endometrial disease
- She will have a poor prognosis for getting pregnant
- She will have a poor prognosis for taking a foal to term
- Attempting to manage this mare will cost a lot of money
You are examining endometrial cytology from a mare. How many neutrophils is too many neutrophils to be normal?
Indications for taking an endometrial biopsy
- Barren mares
- Repeat breeeder mares
- Mares with early embryonic death or abortion
- Anoestrus mares (during breeding season)
- Mares requiring surgery of genital tract
- Pyometra or mucometra
- Fertility evaluation pre-purchase
Endometrial biopsies can inform you of the chances of a mare taking a foal to term.
When can you take an endometrial biopsy?
- Mid-dioestrus = good time as it minimises misleading histological changes
- Biopsy can be taken at any time except pregnancy or when fibrosis of the cervix prevents it
Normal endometrium
Uterine adhesion
Endometrial cyst
This is Equine coital exathema
* Do not breed this mare until the lesions have resolved
* Check for lesions on the stallion’s penis
* Remember the mare may have been cleaned/ tail bandaged etc. by a member of staff with contaminated hands/ equipment
What are the consequences of equine coital exathema?
- Does not result in abortion or infertility
- Stallion may be sore and unwilling to breed
